Pavement markings (e.g., paints, tapes, and individually mounted articles) guide and direct motorists and pedestrians traveling along roadways and paths. Paint was a preferred pavement marking for many years. However, modern pavement marking materials offer significant advantages over paint, such as increased visibility, retroreflectance, improved durability, and temporary and/or removable marking options.
Various types of retroreflective elements have been used in pavement markers. For example, International Disclosure Pamphlet 03038191 describes a composition for a pavement marker in which optical (e.g., reflective) elements are at least partially embedded in a binder that is adjacent to a glass or ceramic core. The particle has a softening point higher than the core material, and the reflective element shows at least an approximately 10% increase in the collision strength when compared with the reflective element where the core does not substantially contain particles.
U.S. Pat. No. 5,942,280 describes a method of making a ceramic retroreflective element having enhanced strength and increased retained reflectivity. The method involves forming retroreflective elements by the following steps: a) providing glass flakes; b) coating said glass flakes with a first barrier layer yielding coated glass flakes; c) providing optical elements; d) optionally coating said optical elements with a second barrier layer; e) blending said optical elements and said coated glass flakes; f) heating said optical elements and said coated glass flakes to spheroidize said flakes while agitating said optical elements and said coated glass flakes; g) further heating said optical elements and said spheroidized glass flakes to partially embed said optical elements in said spheroidized flakes while agitating said optical elements and said spheroidized flakes; and h) cooling said spheroidized flakes having partially embedded optical elements.
Japanese Patent Laid-Open No. 7-109709 describes a construction device including a system having a material shutter to control the coating of the material, an edge plate to decide the width of the coating and a film thickness adjusting mechanism to set the thickness of the coating film at the bottom of a hopper with the material inserted in it to carry out the road markings of specified width on the surface of the road. Japanese Patent Laid-Open No. 7-109709 also described a pavement marking method involving dispersing the glass beads before a coating is applied or the material gets dried. The surface of the glass beads is roughened by allowing the contour particles with large particle diameters to protrude out on the coated surface after forming a pectinate shaped board. The thickness of the film is adjusted by using a coating mixed with the contour particles having a particle diameter larger than the thickness of the coating film.